2H NMR Time Domain Analysis of Ultraslow Reorientations in Supercooled Liquids
A method for evaluating 2H NMR stimulated echo experiments in the time domain is presented. It exhibits a high sensitivity to molecular reorientation mechanisms for small angles. Reorientations with jump angles below 25degrees can be resolved with a precision of approximately 1degrees so that, e.g., rotational diffusion and finite jump angle mechanisms become distinguishable. The method, applicable to isotropic reorientation models, is thought to extend the domain of 2D exchange spectroscopy where the best resolution is obtained in the large angle range of anisotropic reorientational mechanisms. Application to reorientation in the supercooled melt of ortho-terphenyl is presented. These data clearly show that the molecular reorientation of ortho-terphenyl molecules cannot be described by small angular step rotational diffusion. A better parametrization of the experimental data incorporates elementary jump angles in the range of approximately 10degrees. Copyright 1998 Academic Press. Copyright 1998 Academic Press
Geil
B
Fachbereich Physik, Universitat Dortmund, Dortmund, D-44221, Germany
Fujara
F
Sillescu
H